1. Field of Invention
The present invention relates to a virtual universal serial bus (USB) card reader with a peripheral component interconnect (PCI) Express interface, and more particularly to a virtual USB card reader that uses the PCI Express interface as a transmission interface.
2. Description of Related Art
As the science and technology of computers grows in a fast changing manner, a computer tends to be developed with powerful computational functions and a fast speed, and thus the clock of a central processing unit (CPU) is too fast, and the transmission rate of other peripheral equipments cannot catch up with the processing speed of the CPU at all. Even though the CPU continues enhancing its performance, the transmission rate of peripheral equipments cannot be improved much because the overall performance of a computer depends on the whole system. It is necessary to improve the whole computer architecture before the performance of a CPU can be maximized.
However, the data transmission rate depends on the transmission rate of a bus. To enhance the performance of a computer, related manufacturers usually improve the transmission rate of a bus. For example, the transmission rate of an integrated drive electronic (IDE) interface connected to a hard disk drive reaches 160 MB/s; the network line is upgraded from 10 MB/s to 1 GB/s; the transmission rate of the RS-232 is replaced by the 480 Mb/s of the universal serial bus (USB), and the present PCI interface with a transmission rate of 133 MB/s upgrades the transmission rate of its lane to 250 MB/s, which becomes a new-generation peripheral component interconnect (PCI) Express interface. The PCI Express interface further supports a hot-plug control function. Therefore, the PCI Express interface is extensively accepted by users.
Further, the flash memory since its announcement gradually replaces the EEPROM or battery power memory in many portable device due to its charming features including low power consumption, non-volatility, shock resistance, and high-capacity storage. With the advanced semiconductor technologies, the storage capacity and transmission rate of a flash memory grow rapidly and the flash memory replaces traditional storage medium such as a hard disk drive in many applications. However, the present memory card made of flash memories becomes an indispensable product to the general public and the sales volume and types of memory cards are growing due to the popularity of digital cameras, PDAs, and mobile phones.
Most memory cards use a universal serial bus (USB) interface or an integrated drive electronics (IDE) interface as the transmission interface. The transmission rates of the USB or IDE interface are just 480 Mb/s and 160 MB/s respectively, and such transmission rates cannot catch up with the accessing speed of the memory card. Therefore, the applications of the memories are restricted by the USB or IDE interface of the host, and its performance cannot be maximized.
Further, several environment interfaces that integrate editing, coding, debugging, file management and execution are provided in a program development system or a software program, and such environment interface enables a programmer to execute and develop most of the work required for an application program. Therefore, the software executed at the host adopts a specific environment interface and peripheral device for communications, and the peripheral devices must have the environment interface of the host before the instruction from the host can be executed.
Therefore, it is desirable to provide a card reader that eliminates the aforesaid drawbacks.